Terry Pratchett

The bravest person I've ever met was a young boy going through massive amounts of treatment for a very rare, complex and unpleasant disease. I last saw him at a Discworld convention, where he chose to take part in a game as an assassin. He died not long afterwards, and I wish I had his fortitude and sense of style.

By irreducibly complex I mean a single system composed of several well-matched, interacting parts that contribute to the basic function, wherein the removal of any one of the parts causes the system to effectively cease functioning.